Experimental Study On Adsorption Of U(Ⅵ) In Water By Modified Aspergillus Niger

The large amount of uranium-containing wastewater produced in the process of uranium mining has caused serious harm to the environment and human health.Adsorption method has become one of the research hotspots because of its simple operation,low cost and good selectivity.The key of adsorption method is to find a safe,efficient and economical adsorbent.Phytic acid modified Aspergillus Niger(PAN)and succinic acid modified Aspergillus Niger(SAN)were prepared from Aspergillus Niger(AN).The adsorption performance and mechanism of PAN and SAN on low concentration uranium-containing wastewater were discussed.The following results were obtained:(1)Phytic acid modified Aspergillus Niger(PAN)was prepared by water bath heating,and the adsorption and resolution properties of PAN for U(Ⅵ)in water were investigated.The effects of solution p H,temperature,dosage,reaction time and initial concentration of U(Ⅵ)on the adsorption of U(Ⅵ)by PAN were investigated,and the adsorption mechanism was discussed.The results showed that PAN had a good adsorption effect on U(Ⅵ).When the initial concentration of U(Ⅵ)was 5.0 mg/L at p H=5,30 C and the dosage of PAN was 0.3 g/L,the adsorption rate of U(Ⅵ)reached97.13%,which was 34.53% higher than that of unmodified Aspergillus niger.The adsorption time tends to equilibrium after 90 minutes,and the maximum adsorption capacity at 30℃ is 16.19 mg/g.p H is an important factor affecting the adsorption of U(Ⅵ)by PAN.Quasi-second-order kinetics and Langmuir isothermal adsorption model fit the adsorption process well.The adsorption of U(Ⅵ)by PAN is a spontaneous endothermic reaction.The comparison of infrared spectra before and after adsorption showed that-OH,-COOH,-NH,-PO were the main adsorption sites for U(Ⅵ).EDS showed that U element appeared on the surface of PAN after adsorption.Adsorption and desorption experiments showed that PAN had good reusability.(2)Succinic acid modified Aspergillus Niger(SAN)was prepared by esterification chemical method.The adsorption and resolution properties of U(Ⅵ)in water by SAN were investigated.The effects of solution p H,temperature,dosage,reaction time and initial concentration of U(Ⅵ)on the adsorption of U(Ⅵ)by SAN were investigated,and the adsorption mechanism was discussed.The results showed that SAN had a good adsorption effect on U(Ⅵ).At p H=4,25 C,the initial concentration of U(Ⅵ)was 5.0 mg/L,the dosage of SAN was 0.35 g/L,the adsorption rate of U(Ⅵ)reached 90.1%,the adsorption rate increased by about 27%compared with the unmodified one,the adsorption time reached equilibrium after 60 minutes,and the maximum adsorption amount reached 15.21 mg/g at 25 ℃.PH is an important factor affecting the adsorption of U(Ⅵ)by SAN.Quasi-second-order kinetics and Langmuir isothermal adsorption model well fit the adsorption process,which is a spontaneous endothermic process.FTIR comparison before and after adsorption shows that-OH,-COOH,-NH are the main adsorption sites for U(Ⅵ),and the adsorption mechanism is mainly surface complexation reaction.Adsorption and desorption experiments show that SAN has good reusability.